With the increase in population and industrialization, present day water, as supplied by rivers and from the underground, may be polluted by sewage and industrial waste, containing a multitude of germs or pathogens. Moreover, the water as supplied may also be odious and discolored due to the presence of these pollutants. Thus, to obtain water of a good quality, which is suitable for drinking, swimming or industrial use, has comes a problem. Various apparati and processes for disinfecting polluted water have been proposed.
Conventional apparati and processes for removing pollutants from water employ sodium hypochlorite and/or chlorine gas. According to these processes, sewage is disinfected and purified by using an aqueous solution of NaOCl and/or Cl.sub.2 obtained by the electrolytic reduction of an aqueous NaCl solution. There are several drawbacks to these conventional apparati and processes. The apparati are generally complicated and difficult to use. Moreover, the bactericidal effect or the degree of disinfection is not satisfactory. The NaOCl and/or Cl.sub.2 containing solutions are dangerous to work with because a cover layer of chlorine gas is often needed to keep the pH of the water in a desirable range to achieve a desired level of disinfection and purity.
Further, certain pollutants in water, such as phenol when treated with chlorine, produces compounds, such as chlorinated phenol, with odors that are extremely unpleasant and sickening. Moreover, if the water supply is polluted with organic substances, these substances may react with chlorine to produce organic hydrocarbons, which may be carcinogenic.
U.S. Pat. No. 4,790,949 discloses a process for the preparation of a disinfectant for water with improved disinfecting and bactericidal effects. The disinfectant is prepared by electrolyzing an aqueous NaCl and NaOCl solution to obtain an aqueous NaOCl solution enriched with chlorine at a constant pH value but without the presence of free chlorine gas.
Chinese Patent CN 2,037,361U discloses an apparatus for supplying disinfected drinking water continuously. The structure of the disclosed apparatus is simple. However, it suffers from the fact that NaOCl is used as the principal disinfectant with all of the ensuing disadvantages.
In order to overcome these drawbacks, an apparatus and method using ClO.sub.2 gas as a disinfectant for treating polluted water had been disclosed. It was found that the oxidizing potential of ClO.sub.2 is much higher than chlorine gas and can be used to effectively kill germs or pathogens and remove discoloration and odor from the water. At the same time, the danger of producing carcinogens such as organic hydrocarbons is avoided.
However, the prior disclosed ClO.sub.2 generator has other disadvantages. The process is inefficient and a low rate of ClO.sub.2 is generated. This results in the need for an excessive amount of work to determine the level of bacteria and the presence of pollutants because the results are needed to adjust the working condition of the apparatus to achieve a desired level of disinfection. For the above reasons, up to the present, it has been difficult to directly and continuously supply sufficient disinfected water suitable for daily and industrial use, for example with less than 3 colibacillus/L, at a sufficient rate.
The object of the present invention is to provide an apparatus for disinfecting continuously and effectively the polluted water by using ClO.sub.2.
The another object of the present invention is to provide a satisfactory process of using ClO.sub.2 to continuously and effectively disinfect polluted water.